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IT Support & Hardware · Intermediate

Clear CMOS

Resetting stored firmware settings to factory defaults, usually by jumper, button, or removing the battery.

Definition

Clearing CMOS fixes problems caused by bad settings, failed overclocks, or a forgotten firmware password on many desktops. Methods include shorting a CLR_CMOS jumper, pressing a rear-panel button, or removing the coin cell with the system unplugged. Laptops and business systems may store supervisor passwords in separate nonvolatile memory that is not cleared this way.

Example

After a failed memory overclock prevents POST, short the CLR_CMOS pins for 10 seconds.

Exam tip

Always unplug power before clearing CMOS; some business laptop passwords survive a CMOS clear.

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